NAME

       ZSCAL - scales a vector by a constant.

SYNOPSIS

       subroutine zscal(n,za,zx,incx)

           c                          scales a vector by a constant.

           c                          jack dongarra, 3/11/78.

           c                          modified   to  correct  problem  with  negative  increment,
                                      8/21/90.

           double                     complex za,zx(1)

           integer                    i,incx,ix,n

           if(n.le.0)return

           if(incx.eq.1)go            to 20

           c                          code for increment not equal to 1

           ix                         = 1

           if(incx.lt.0)ix            = (-n+1)*incx + 1

           do                         10 i = 1,n

           zx(ix)                     = za*zx(ix)

           ix                         = ix + incx

           10                         continue

           return

           c                          code for increment equal to 1

           20                         do 30 i = 1,n

           zx(i)                      = za*zx(i)

           30                         continue

           return

           end

PURPOSE